How can a wild animal like a mountain lion be better for our health? We have all heard about the web of life, how all things are connected, and that there is a natural balance within an ecosystem. Pumas show us how removing part of that system shifts that balance and creates a system that is more detrimental to us people.
Let’s first look at the web of life that a puma lives in:
The web of life for a Puma (very simplified)
In this very simplified (though accurate) system, pumas feed primarily on deer, which in turn feed on grass. Besides mountain lions, deer only have humans as predators (and sometimes the odd coyote), but are parasitised by lots of organisms including ticks. The mountain lions keep deer numbers in check, which in turn keeps tick numbers in check, as does it keep grass from being under-abundant. (If you are a school teacher and would like to incorporate this concept into your curriculum, contact Felidae Conservation Fund for their CAT Aware Program).
Let’s look at this same system on the east coast of the United States, where Cougars are no longer found.
Web of life without the Puma
Without the pumas, deer numbers have grown tremendously, these animals in turn feed on the local vegetation, which leads to overgrazing since their numbers are too large. More importantly for us people, because there are more deer, there are more ticks that feed on those deer.
This is where the health aspect comes in. Ticks carry disease, including Lyme disease. With more ticks present, there may not be a larger percentage of ticks that carry Lyme disease but there will be a larger number of individuals that are vectors of it. Due to the fact that cougars are not controlling deer numbers on the east coast, more Lyme disease carrying ticks are around, which leads to a higher rate of incidence for the disease in the area.
Let me illustrate the point with some maps.
Tick species ranges that carry Lyme disease in the US
In the US, both the Black-legged Tick (Ixodes scapularis) and the Western Black-legged Tick (Ixodes pacificus) carry and transmit Lyme disease.
This is the area in which Lyme disease has the highest incidence rate (or, where it happens the most):
The fifteen states with the highest incidence rate of Lyme disease in the US (see Lyme Disease Association Analysis) — the darker the red the higher the number of incidences
As you can clearly see, the highest chance of infection is limited to the east Coast.
Now let’s look where Pumas currently live in accordance with the above data:
Mountain Lion presence and their relation to Lyme disease infection
Even though Lyme disease and their vectors are present on the west coast of the US, mountain lions keep the tick numbers low (by keeping the deer numbers lower), therefore creating an overall healthier system for people. More mountain lions eventually means a lower chance of getting Lyme disease.
Historically, cougars used to occupy the east coast where Lyme disease is so prevalent now, but they were extirpated from the region in the early 1900’s. Could a case be made for re-introducing cougars to the east coast, now that they have been gone from the region for hundreds of years? Is there even space for them? Even though the western United States has greater areas of fully protected land, the eastern states still have plenty of habitat for pumas as well.
US population density – Copyright Ian Offord
The population density map shows that cougars have no space left on the eastern coast, nor would you want them to wander into New York City or Boston, but once you are more inland, the population density is low enough where you can have successful co-existence between these cats and people. Having an action plan would help of course but even naturally, pumas are moving more and more east as time passes. Maybe sooner than later, Lyme disease will be less of an issue in the States, and all due to a wild cat.